Edema is a localized or general swelling caused by the build-up of fluid within body tissues. It most commonly occurs in the feet and legs, where it also is referred to as peripheral edema. However, excess fluid can occur anywhere in the subcutaneous tissue or lungs. This excess fluid may be the result of any number of causes. For example, it may be the result of poor blood circulation, lymphatic system failure, disease of the heart or kidneys, reduction in the amount of blood protein (e.g., which may occur as a result of cirrhosis), chronic nephritis, malnutrition, or toxemia of pregnancy (preeclampsia). Some other causes of edema are use of birth control pills, premenstrual syndrome, sunburn, and an imbalance of sodium and potassium. Localized edema may also result from injury or infection.
Diuretics are most typically used to treat edema. Some diuretics are used to treat Meniere's disease and other types of vertigo where excessive fluid pressure builds up within the inner ear. Some diuretics are used to treat glaucoma, where excessive fluid pressure builds up within the eyeball. Similarly, some diuretics are used to treat pulmonary edema, where fluid accumulates in the lung tissue. Diuretics may also be used to treat high blood pressure (i.e., hypertension), overdosage of certain drugs, and cystic fibrosis.
There are a number of compositions commercially available as diuretics. These include ethacrynic acid, bumetanide, furosemide, muzolimine, spironolactone, torsemide, triamterene, and tripamide. These diuretics are most commonly delivered as an oral dosage form (e.g. as a pill, capsule, or tablet), or delivered intravenously. Disadvantages of oral dosage forms include a delay in the onset of activity and loss of drug therapeutic effect due to hepatic first-pass metabolism. Intravenous delivery, while typically more effective than oral delivery (particularly for loop diuretics), is often painful and inconvenient. Currently, intravenous delivery is the only option available for exacerbations of congestive heart failure. It would be desirable to provide other dosage forms and routes of administration with improved properties.